The present invention relates to a stentless aortic valve bioprosthesis constructed of single or multiple sections of biological tissue to minimize coronary obstruction. The valve is implantable with a single suture row.
Various stentless valves have been advanced. Tissue valves are typically used in those patients for whom long term anticoagulation is contraindicated, or who may be difficult to maintain on anticoagulation therapy. The stentless valves typically are constructed in a manner that requires a double row of sutures for fastening, one along an inflow edge and one along an outflow edge, and require a substantial amount of time for implanting.
Existing state-of-the-art valvular prostheses have one or more of the problems of introduction of foreign tissue; physical obstruction; and implantation trauma. The implantation trauma is accentuated when there is extensive suturing, for example, two suture rows.
Stentless aortic valves presently on the market have had problems because the valves have tall bodies, leading to obstruction of the coronary ostia or coronary sinuses, requirements for double suture rows, and extended implant times. Some of the valves that are on the market also include synthetic materials in the design.
The present invention relates to an aortic or pulmonary stentless valve constructed entirely of crosslinked biological tissue, which minimizes obstructions and permits implantation with a single suture row in significantly less time than that needed for implanting existing valves. The valve preferably is constructed of a single or of multiple pieces of bovine biological tissue. In a preferred form, multiple segments of tissue are formed in such a way to provide for complete coaptation of the valve leaflets to prevent regurgitation or insufficiency, and to provide full valve opening to allow for a maximum effective orifice area. The exterior of the valve is preferably conical in shape, which aids in implantation and reliability. The conical shape results in the valve being larger in diameter at the outflow end than at the inflow end.
The preferred form of the invention is an assembly of three leaflets of biological tissue that are attached to adjacent leaflets at the commissure region, preferably through the use of tissue reinforcing commissure posts and a separate reinforcing rim strip. The rim strip is sutured on the exterior of the leaflets when it is used and provides a suturing reinforcement at the perimeter or base of the valve. The suturing used for constructing or assembling the valve is on, or in, non critical areas of the tissue to enhance valve durability.
The biological commissure reinforcement posts or pads are sculpted to be applied at each commissure by slipping over adjoining edge portions of mating edges of the leaflets to strengthen the attachment and aid in the distribution of stresses at the critical areas where the adjacent valve leaflets join. The rim strip is a biological tissue reinforcement that has portions sutured to the posts and leaflet edges at the commissural area of the leaflets, and sutured to the base edges of the leaflets, forming the base ring of the valve. The rim strip is on the outside of the leaflets, to provide reinforcement to the rim formed by the base ends of the leaflets, and thus aids in the attachment of the valve to the patient""s aortic annulus. The double layer of tissue at the rim provides a suture attachment site that is designed for strength. The design is anatomical in that it resembles the human aortic valve for a close fit, and needs only a single suture row for implantation. The low profile valve is short along the flow axis and of minimal width, so it is anatomically easy to handle.
Trimming biological tissue to the desired size and shape for constructing the valve can be done readily. The assembly of the valve parts requires minimal time, thereby reducing manufacturing costs. Since the valve is made entirely of biological tissue, there are no problems associated with synthetic material performance. The implantation is easily carried out in significantly less time than that needed for existing prostheses.
Flexibility of the tissue leaflets and the reinforcement posts and rim in the commissure areas where the leaflets open and close permits a wide opening to thus reduce pressure drop across the valve once implanted. The valve leaflets are less prone to tear because of cushioning by the valve parts. The conical design and the flexibility of the tissue leaflets also ensures satisfactory leaflet coaptation to reduce any regurgitation or insufficiencies. Further the fully flexible valve can be used in most aortic valve pathologies. The attachment rim fits all normal and abnormal annulus shapes for implantation.
The bovine biological aortic stentless valve of the present invention has an anatomical profile. The sewing cuff or rim is part of the leaflets and may include a reinforcing rim strip. It has a conic shape to be accommodated in most aorta geometry, and prevent valve insufficiency. The sewing area is easily penetratable with a needle, being no more than about 2 mm thick. The valve flexibility permits it to follow the contour of the patient""s aortic annulus, thus remaining beneath both coronary sinuses. The internal to external diameter ratio is excellent and better than present designs since the cuff or rim is not covered with fabric, thus resulting in a more hemodynamic valve. The cuff or rim is an intrinsic part of the leaflets and follows the patient""s annulus.
The present valve is all biological and does not have synthetic material, such as a polyester cloth covering. The valve has a low commissural profile that simulates natural valve geometry. There is a need of only one suture row for implantation and while placing the sutures, the leaflets are preserved from needle injury since the components are all fully in the surgeon""s view. The valve cuff or rim may be reinforced with a biological strip or tape without increasing the cuff or rim width or affecting the effective orifice area. The time of surgery is reduced significantly, and may be in the range of one-third to one-half of the implantation time required for existing valves. The reduced profile of the valve provides a superior view for the surgeon. This, in turn, helps in reducing implantation time, injury to leaflets, valve misalignment and occlusion of the ostia. Further, the problems associated with occlusion of the coronary sinuses is avoided, since the present valve leaves the coronary sinuses substantially unobstructed. Thus, situations caused by occlusions of the coronary sinuses or ostia are not likely to occur.
The valve can be offered with a specific holder, just as the existing replacement heart valves.